Abstract
Afferent projections to the mediodorsal and anterior thalamic nuclei in the cat were studied by means of stereotaxic injection of neuronal tracers (horseradish peroxidase and fluorochromes). Acetylcholinesterase reaction was studied, as well as horseradish peroxidase and NADPH-diaphorase colocation in neuronal bodies which send and receive projections to and from the mediodorsal thalamic nucleus. Based on the connectivity and histochemistry findings, the possibility that prion agents responsible for fatal familial insomnia spread from the mediodorsal and anterior thalamic nuclei through a retrograde pathway is discussed. The possible pathophysiological implication of nitrergic systems in fatal familial insomnia is also considered.